Monthly Archives: February 2013

Education, Physics

The physics of heavy metal \m/

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moshpit
Wetwebwork from London, U.K.

The American Physical Society March Meeting 2013 (Monday–Friday, March 18–22, 2013, Baltimore, Maryland), is going to be focused on the physics of behavior. One abstract caught my eye…

Mosh pits and Circle pits: Collective motion at heavy metal concerts
Matthew Bierbaum , Jesse L. Silverberg , James P. Sethna and Itai Cohen

Heavy metal concerts present an extreme environment in which large crowds (∼10^2−10^5) of humans experience very loud music (∼130dB) in sync with bright, flashing lights, often while intoxicated. In this setting, we find two types of collective motion: mosh pits, in which participants collide with each other randomly in a manner resembling an ideal gas, and circle pits, in which participants run collectively in a circle forming a vortex of people. We model these two collective behaviors using a flocking model and find qualitative and quantitative agreement with the behaviors found in videos of metal concerts. Furthermore, we find a phase diagram showing the transition from a mosh pit to a circle pit as well as a predicted third phase, lane formation.

The preprint
Their presentation is based on a preprint on the arXiv “Collective Motion of Moshers at Heavy Metal Concerts” [1]. Using videos publicly available online, they study the highly energized collective motion of attendees at heavy metal concerts.

They model the behavior at heavy metal concerts and find a disordered gas-like state, commonly known as a mosh pit and an ordered vortex-like state known as a circle pit.

References
[1] Jesse L. Silverberg, Matthew Bierbaum, James P. Sethna, Itai Cohen, Collective Motion of Moshers at Heavy Metal Concerts, arXiv:1302.1886 [physics.soc-ph]

Link
Mosh pits and Circle pits: Collective motion at heavy metal concerts

Education, General Mathematics

e-Mentoring Network in the Mathematical Sciences

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maths blog

Ricardo Cortez of Tulane University, and Dagan Karp of Harvey Mudd College have set up a blog that address questions that students, postdoctoral researchers and junior faculty may have regarding their advancement in mathematics. The blog is part of the American Mathematical Society blogs and I am sure will become a very useful resource.

cortez
Ricardo Cortez		 Karp
Dagan Karp

An extract from the first post

Two years ago, at the 2011 Joint Mathematics Meetings in New Orleans, I attended a panel discussion sponsored by the MAA. The session title was “Good intentions are necessary but not sufficient: Steps toward best practices in mentoring underrepresented students” and one of the goals of the session was to propose specific ideas that could be implemented as a result of the comments made by panelists and participants. In other words, there was a desire to go beyond offering opinions and advice. There was a desire to come up with concrete actions. I really liked the idea.

Ricardo Cortez, Building a community of mentors

Link
e-Mentoring Network in the Mathematical Sciences

Education, General Mathematics, Physics

Lords publishes report on Open Access

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The House of Lords Science and Technology Select Committee has published a report focusing on the implementation of the Government Open Access policy.

lords
The debating chamber of the House of Lords in the Palace of Westminster

Things the report covers includes arrangements for article processing charge funds, international issues and risks for learned societies, such as the Institute of Physics and the London Mathematical Society.

Link
The implementation of open access (Opens PDF)

Physics

Looking for unparticles using the Earth's interior?

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Prof. Larry Hunter and colleagues at Amherst College in Massachusetts, together with Jung-Fu Lin of the University of Texas, Austin, have used the Earth to put bounds on long-range spin-spin forces associated with the virtual exchange unparticles [2].

Background
Recall that intrinsic angular momentum, or spin, of a particle of what gives rise to a particle’s magnetic moment and it is the interaction between spins that generates a magnetic field. In quantum electrodynamics the standard understanding of the interactions between the spins is in terms of the exchange of virtual photons.

In 2007, Howard Georgi of Harvard University proposed the existence of unparticles, which represents an as of yet undiscovered scale invariant sector to the standard model [1]. The exchange of unparticles would lead to a new type of spin–spin interaction. It is this new interaction that Larry Hunter and colleagues have been looking for.

Unparticles and the crust?
Prof. Hunter and colleagues created a map of the Earth’s polarized electron spin density. Then they calculated the potentials associated the possible spin interactions and integrated this across the whole of the Earth. The effect of these potentials on two detectors that can probe long-range interaction between spins in the Earth’s interior was worked out.

Using this they were able to place new upper bounds on the forces due to the exchange of unparticles. Improvements in sensitivity as compared to existing laboratory experiences is by a factor of a million.

Hunter

In our obscure business of precision measurements it might take a decade to improve the sensitivity of an experiment by an order of magnitude, so using just laboratory sources it might have taken 60 years to get to the limits we did.

Prof. Larry R. Hunter

References

[1]Howard Georgi (2007). “Unparticle Physics”. Physical Review Letters 98 (22): 221601

[2] Larry Hunter Joel Gordon, Stephen Peck, Daniel Ang and Jung-Fu Lin, Using the Earth as a Polarized Electron Source to Search for Long-Range Spin-Spin Interactions, Science 22 February 2013: Vol. 339 no. 6122 pp. 928-932

Links
Search for ‘unparticles’ focuses on Earth’s crust (Physics World)

General Mathematics, Physics, Research work

International Conference on Mathematical Modeling in Physical Sciences

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modeling

The International Conference on Mathematical Modeling in Physical Sciences is to be held at Prague, Czech Republic during September 1-5, 2013. The conference aims to promote the knowledge and the development of high-quality research in mathematical fields that have to do with the applications of other scientific fields and the modern technological trends that appear in them, these fields being those of Physics, Chemistry, Biology, Medicine, Economics, Sociology, Environmental sciences etc.

Topics
ICMSQUARE-2013 topics encompass, but are not restricted to, the following areas:

  • mathematical modeling in Fundamental Physics
  • evolutionary computation
  • complex physical and technical systems
  • software and computer complexes for experimental data processing
  • qualitative modeling including fuzzy and iterative approaches to modeling
  • nonlinear problems
  • computational chemistry, biology, and biophysics
  • new generation computing tools, distributed scientific computing
  • computational modeling in engineering and science
  • multiscale modeling, multiphysics modeling
  • progress in discretization methods
  • financial mathematics and mathematics in economics etc.

Venue
The conference is to be held at Prague, Czech Republic during September 1-5, 2013 at the Conference Center of the Orea Hotel Pyramida 4*. The hotel is situated by Hradcany and Strahov, within walking distance from the Prague Castle, Loreta, Strahov monastery and the Lesser Town. The Conference Center of the Hotel Pyramida offers ten fully air-conditioned conference rooms. Together they can accommodate up to 1100 people.

Registration and submission
All the actions related to the IC-MSQUARE 2013 (paper submission, registration etc) may be completed via the Conference website at http://www.icmsquare.net.

Important dates:

Tuesday, 30 April 2013, Abstract submission deadline
Wednesday, 15 May 2013, Notification of acceptance
Friday, 31 May 2013, Early registration deadline
Wednesday, 31 July 2013, Full paper review submission deadline
Sunday, 1 September 2013, Conference opening

Organizing committee

Prof Theodosios Christodoulakis
Dr Elias Vagenas
Prof Dimitrios Vlachos

General, General Mathematics

The London Mathematical Society response to inquiry on Open Acces

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lms
The London Mathematical Society has responded to the House of Lords Science and Technology Select Committee inquiry into open access publishing. The response can be found below.

We have long been concerned about the threat to our Society from the implementation of open access policies which seek to reduce the level of library sales by making the content of journals available to readers through alternative routes.

The Institute of Physics has also responded, follow the link below.

Link
RESPONSE FROM THE LONDON MATHEMATICAL SOCIETY (opens PDF)

Institute of Physics response to a House of Lords Science and Technology Committee inquiry (opens PDF)

Astronomy, General, Physics

Take that Einstein…I mean, take that cranks!

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einstein

… all of the available constraints on the validity of the founding principles of SR and GR have so far failed to crack any faults in these century-old theories, which thus remains the standard against all competitors so far.

Orfeu Bertolami and Jorge Páramos in [1]

I like the above quote. It is rather an inescapable that Einsteinian relativity works well.

Objections to relativity
I posted, about a year ago now, on the experimental status of Einsteinian relativity, you can read it here.

Whatever the faults with general and special relativity, philosophical or real, today we have no other theory of space, time and gravity that has the experimental success of Einstein’s theories.

Most of the “objections” to special and general relativity stem from not really understanding what the theory is saying, or indeed what a theory really is. Analogies and popular science accounts seem to also be the root of a lot of misunderstandings.

Other good references on the experimental status of relativity include [2,3,4].

The failings of general relativity
It is not true that anyone really expects general relativity to be the final say on gravity. The issues as they stand include:

  • The existence of singularities
  • The cosmological constant problem
  • Incompatibility with standard quantisation methods
  • Dark energy

All these problems only really tell us that general relativity is not a complete theory in the sense that there is physics that it cannot accurately explain.  This is not grounds for dismissing general relativity as it is a very accurate model of gravity for a huge range of phenomena.

 

References
[1] Orfeu Bertolami and Jorge Páramos, The experimental status of Special and General Relativity, arXiv:1212.2177v1 [gr-qc]

[2]Orfeu Bertolami, Jorge Páramos, and Slava G. Turyshev. General theory of relativity: Will it survive the next decade? In Lasers, Clocks, and Drag-Free: Technologies for Future Exploration in Space and Tests of Gravity. Springer Verlag, 2006; gr-qc/0602016.

[3]Clifford M. Will. The confrontation between general relativity and experiment. Living Reviews in Relativity, 9(3), 2006.

[4]Will, Clifford M. (2006). Was Einstein Right? Testing Relativity at the Centenary. Annalen der Physik 15: 19–33

General Mathematics, Mathematical Art

Some Julia sets

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julia1

Above is the Julia set of \(F_{c} = e^{z^{3}}\) at the point \(– 0.621\).

julia2

Above is the Julia set of \(F_{c} = (1+z+ \frac{z^{2}}{2})Exp[z^{-3} -z]\) at the point \(-0.6 -i\).

julia3

Above is the Julia set of $latex F_{c} =-\frac{\cosh \left(-z+1+\frac{1}{z}-\frac{1}{z^2}+\frac{1}{z^3}\right)}{|z|}+\sinh
\left(-z+1+\frac{1}{z}-\frac{1}{z^2}+\frac{1}{z^3}\right)$ at the point \(-(0.62-0.4 i)\).

I have posted other Julia sets here.

You can find out more about Juila sets here.